My rusty school Irish always had this as "Dia dhuit", and apparently that is how it's spelt in Munster and Connacht, but not in Ulster and standard Irish follows the Ulster dialect, in this case at least. I doubt anybody minds one way or the other.

I dont know how to get this message through to the powers that be, so I am recording my dissatisfaction here. I have now had a streak of at least 75 days. Duolingo are not recording my efforts correctly. Duo lingo have now confused me so much that I am now not sure if it is a 75 or 76 day streak, on this the 26/07/18 at 1am in Cuba. But I am not on a one or two day streak that is definite.